At least 40 residential and commercial neighbourhoods in Chennai were inundated in the heaviest rains to lash the Tamil Nadu capital since 2015, prompting authorities to issue a preliminary flood alert and to release 500 Cusecs of water from the Puzhal and Chembarambakkam reservoirs. Data from two rain recorders shows that the city and suburbs had received 21.5 cm and 11.3 cm rains respectively by 8:30 am on Sunday. In November 2015, Chennai recorded 24.6 cm rainfall in 24 hours, surpassing the previous record of 14.2 cm from November 2005.

In November 1976, Chennai recieved 45.2cm of rainfall and another record rainfall, in two days, was registered in the same month of 1985.

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Monsoon Rains

Chennai’s monsoon typically begins between October 10 to 20, brought on about by easterly winds from Northeast Monsoon, starting mid-October. The Northeast Monsoon, also known as the ‘primary monsoon of Tamil Nadu,’ brings sufficient rains to the state when all other states depend on the South West monsoon for rains that sets in from May, June and July. If the South West monsoon helps Tamil Nadu maintain ground water tables, the North East monsoon elevates the same, accounting for 60% of the annual rainfall in coastal districts and about 40-50% in the interior districts.

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Meanwhile, the meteorological department has predicted moderate rain in the coming days ahead of a likely formation of low pressure over the Bay of Bengal moving towards the northern Tamil Nadu coast.

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“It is likely to become more marked during subsequent 48 hours and move towards the north Tamil Nadu coast,” Regional Specialised Meteorological Centre – Tropical Cyclones, said in a statement. It also predicts squally winds of 40 kmph to 50 kmph gusting to 60 kmph over the sea from November 9, and along and off the Tamil Nadu coast and south Andhra Pradesh coast from November 11 and 12.